The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Engines such as diesel engines produce particulate matter (PM) that is filtered from exhaust gas by a PM filter. The PM filter is disposed in an exhaust system of the engine. The PM filter reduces emission of PM that is generated during combustion.
Over time, the PM filter becomes full. During regeneration, the PM may be burned within the PM filter. Regeneration may involve heating the PM filter to a combustion temperature of the PM. There are various ways to perform regeneration including modifying engine management, using a fuel burner, using a catalytic oxidizer to increase the exhaust temperature with after injection of fuel, using resistive heating coils, and/or using microwave energy.
The increased temperature of the PM filter during regeneration may exceed the temperature at which the collected PM combusts without exceeding the temperature at which the PM may be damaged. For example, PM from a diesel engine may combust at temperatures of 550 degrees Celsius (° C.) or above while a PM filter such as one employed in a full-size pickup truck may be damaged at temperatures as low as 800° C.
High PM filter temperatures may also occur in situations other than regeneration. Fault conditions may exist such that the PM filter temperature unintentionally rises during vehicle operation to a level that may damage the PM filter if continued for a period of time. Examples of other fault conditions that may occur in a diesel vehicle include an exhaust gas recirculation (EGR) valve leaking or sticking open, or leaks in the EGR gasket, turbocharger, intake manifold gasket, fuel injectors, charge air cooler (CAC), CAC pipes, or CAC hoses. In general, the PM filter temperature may rise to a potentially damaging level during any underboost or overfueling condition that results in abnormally high exhaust gas temperatures.